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[82.17.115.212]) by smtp.gmail.com with ESMTPSA id u11-20020a5d6acb000000b0022afedf3c87sm13662057wrw.105.2022.10.12.05.41.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Oct 2022 05:41:02 -0700 (PDT) Date: Wed, 12 Oct 2022 13:41:01 +0100 From: Aaron Tomlin To: Hillf Danton Cc: frederic@kernel.org, mtosatti@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, atomlin@atomlin.com Subject: Re: [PATCH v8 5/5] tick/sched: Ensure quiet_vmstat() is called when the idle tick was stopped too Message-ID: <20221012124101.zod6m2brlzpgx6nb@ava.usersys.com> X-PGP-Key: http://pgp.mit.edu/pks/lookup?search=atomlin%40redhat.com X-PGP-Fingerprint: 7906 84EB FA8A 9638 8D1E 6E9B E2DE 9658 19CC 77D6 References: <20220924152227.819815-1-atomlin@redhat.com> <20220925010511.1482-1-hdanton@sina.com> <20221003124435.1769-1-hdanton@sina.com> MIME-Version: 1.0 In-Reply-To: <20221003124435.1769-1-hdanton@sina.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iMmURJUs; spf=pass (imf29.hostedemail.com: domain of atomlin@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=atomlin@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1665578465; a=rsa-sha256; cv=none; b=zXkattGv0INBz++NTB6tuCZB3sXn7PMGut6S0xxrYgeLw2r5BgBN4UsXhrUBKuiBtXLyw+ uak8UfwGGYSo1PdqBYPLLUCK2AMszeD91clMUN08kNXcQgdojHI2i9VRsMppbi6ZE6JiYf HmpSy7sydgNQpfVBfu5YBUoUaPwhY/M= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1665578465; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=bv29RAREeBAbvgsCg22WvWf89lmnsctG7Ho4iszploI=; b=1i0Lk8EpUoHGNzKxhuEEq0RMrjUuQHpayOecJvu3pB/2S2Ly8NW3wiql7XNjNXVx/H67ko VBhiTitrBbpDtkRPQzkSwq7IeQkWIhIPdE40hg6WI3fHn9YuxHweVsx3hYILjGyAshb/Y1 lzuz1mnGWNyR/CvZQlVKVbC8AvF20EM= X-Rspam-User: X-Stat-Signature: mryrqodtr3khe46fgdnhnhtqc9xfrqz9 X-Rspamd-Queue-Id: 70E7812002B Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=iMmURJUs; spf=pass (imf29.hostedemail.com: domain of atomlin@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=atomlin@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam07 X-HE-Tag: 1665578465-356007 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > Given work canceled because per-CPU pages can be freed remotely from > housekeeping CPUs (see patch 3/5), what is added here is not needed. Hi Hillf, Firstly, apologies for the delay! The concern is to ensure CPU-specific vmstat counters are reset and folded into NUMA node and zone specific and global counters too before entering idle. It is necessary to invoke quiet_vmstat() on return to idle even if the scheduling-clock tick has been previously stopped. Please refer to the complete scenario I described again. If I understand correctly, indeed the remote drain/or free of zone CPU-specific pages can be initiated by a "housekeeping" CPU i.e. refresh_cpu_vm_stats(true) via a worker thread/or kworker, yet the actual free will only occur when the nohz_full CPU exits idle code and calls schedule_idle(). Kind regards, -- Aaron Tomlin